A critical and a continuous need exists for a delivery system for orally administering a beneficial agent in the colon. The oral delivery system is needed and it would be of a particular value in the management of ailments, diseases, or inflammation of the colon that require colon-targeted administration of a beneficially active agent. That is, the oral delivery system would have a therapeutic value where therapy indicates topical-colon administration of a beneficial agent to an affected colon site. A critical and a continuous need exists also for an oral delivery system that releases an active agent for systematic absorption of the active agent from the colon. The need for such a delivery system exists where it is therapeutically indicated to delay systemic absorption of the active agent for a predetermined period of time. More specifically, the need exists for a system that releases the active agent at about the time therapy is needed by a patient. An oral delivery system that releases an active agent for systemic absorption only in the colon at a preselected time would have a practical value in the management of patients with asthma, arthritis or inflammation. For example, the delivery system would be administered orally to the patient at bedtime with the system passing through the stomach and the intestine during the night and arriving at the colon, where it commences release in the colon the active agent in the morning, thereby providing the patient with the desired therapy at the appropriate time.
Prior to this invention, tablets, capsules, and the like, were orally administered for dispensing an active agent throughout the entire gastrointestinal tract. However, for some drugs a considerable amount of the active agent dispensed by the tablets and the capsules is inactivated by the stomach because of the acidic and enzymatic environment of the stomach. Additionally, most agents are metabolized or absorbed in the small intestine from such immediate release forms. Consequently, very little of the active agent is available for producing a therapeutic result in the colon. The delivery of active agents through the rectum using suppositories or enemas often leads to colon therapy; but rectal administration is inconvenient and messy, and it is not readily accepted by the patient population. Also, agent delivery from suppositories cannot reach most of the colon as it is self-limited to the immediate area of administration.
It is immediately self-evident in view of the above presentation, that a need exists for an oral system that delays the onset of delivery for a period of time for the system to reach the colon. Such a period of time corresponds to the time required for the system to transit through the stomach and small intestine and commence delivery of the active agent about the time the system arrives at the colon.